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Enclosure 3- San Miguel River Instream Flow Recommendation Biological Flow Recommendations Overview of Recommended Flow Rates The Bureau of Land management (BLM) and the Colorado Division of Wildlife (CDOW) are recommending 325 cubic feet per second, high flow period (spring /summer), and 115 cubic feet per second, low flow period (fall /winter), based on their data collection efforts. These flow recommendations are based on the physical and biological data collected to date and do not incorporate any water availability constraints. 325 cubic feet per second is required to maintain a reasonable amount of bluehead and flannelmouth sucker usable spring and summer habitat, in addition to maintaining the three principal hydraulic criteria of average depth, average velocity and percent wetted perimeter at adequate levels. 115 cubic feet per second is required to maintain a reasonable amount of bluehead and flannelmouth sucker usable fall and winter habitat, in addition to maintaining two of the three principal hydraulic criteria. The recommended flow values were determined using the best professional judgment of the CDOW and the BLM biologists and hydrologists. The CDOW and the BLM professionals reviewed and evaluated the results of the Physical Habitat Simulation ( PHABSIM) Methodology and River Habitat Simulation (RHABSIM) software PHABSIM /RHABSIM analysis. They also reviewed the R2CROSS analysis, using standard hydraulic criteria. The BLM and the CDOW staff compared results from their PHABSIM /RHABSIM data analysis with their R2CROSS analysis. Using the results from the PHABSIM/RHABSIM data analysis, the maximum amount of usable habitat for bluehead suckers was produced at a flow of 500 cfs and for flannelmouth suckers at a flow of 325 cfs. The R2CROSS analysis indicated that a spring/summer flow of approximately 650 cfs was necessary to meet all three of the critical hydraulic criteria at this site and a fall /winter flow of 115 cfs would meet 2 of 3 of the hydraulic criteria. Comparison of PHABSIM and R2Cross Results The CDOW and the BLM are recommending -that a flow of 325 cfs, for the time period of April 15 through June 14, is the minimum amount necessary to preserve the natural environment to a reasonable degree, for this reach of the San Miguel River. This is based on the assumption that 325 cfs would preserve 90% of the weighted useable area available to the bluehead sucker and 100% of the weighted useable area available to the flannelmouth sucker. BLM and CDOW hydrologists and biologists also believe a flow that maintains adequate bluehead and flannelmouth sucker habitat should also maintain adequate roundtail chub habitat.